Electrical contacting device



July 3, 1962 A. E. ANDERSON 3,042,778

ELECTRICAL CONTACTING DEVICE Filed April 15, 1959 flerfEMnrm .Zrveab 557 /'-G;; W La Qk 4 fitauyi United States Patent This invention relates to contacting electrodes and more particularly to electrical contact elements combining integral arc dispersion with an arrangement wherein the planes of two flat contacting surfaces are caused to meet automatically at all times in exact coplanar relationship. I

Electrical contacts are employed in everyday life in a very wide variety of apparatus. For instance, a high power circuit breaker of a power transmission line system is an extreme example of a contact; the contacts of a microswitch represents an extreme of another kind. In the latter, the power controlled is so low that usually no serious problems are presented in electrode design. However, the control of higher power levels by electric contacts involves problems of all kinds, particularly when the contacts must function reliably over a long period of time. In circuits requiringa multiplicity of controlling contacts, the failure of a single contact may have serious consequences. The operation of electrical contacts is also the limiting factor in the design of many electrical control systems, and the development of automation in modern industry has further increased the need for reliable contacts.

There is also considerable variety of electrical equipment using electrical contacts which specifically must be frequently opened and closed in a very short period of time, which have to be capable of handling current surges of relatively large magnitude. A partial list would include various kinds of circuit breakers, timers, motor starters, controllers of all kinds, advertising flashersthe most common being the conventional ignition system for internal combustion engines. The last mentioned is a representative example of the rapid making and breaking of an electrical circuit and of the problems of electrical contacts. For this reason the invention to be described herein will be with particular reference to such applications in internal combustion engines. It is to be understood, however, that the invention has an unlimited application to all varieties of electrical and electronic equipment which use electrical contacts and wherein the basic features of the invention can be used to improve the life and operating efiiciency of t-he cont-acts- The purpose of all electrical contacts is to perform the three operations of making a circuit, maintaining a circuit, breaking the circuit and to repeat these operations at intervals which in some cases may be extremely short, and others as long as years. As might be ex-,

ected, the particular physical forms and operating conditions of the electrical contact depend on the function it has to perform. The design may vary from the large circuitbreaker to the delicate so-called electrostatic contacts o f electronic circuits. I

The usual problem, heretofore, has been that of finding and arranging electrode materials which under spe'citied operating conditions will produce a low resistance contact when required and continue to doso over-a long 7 operating life. The outstanding cause of unreliability is the destruction of the initially smooth s-urfaces of the contacting electrodes leadingto extensive deformation of the respective surfaces. This makes electrical contact bad or impossible. The deformation is produced by p-rogressive erosion of the electrode material during use. Such erosion occursslowly or rapidly, on a micro scale or over large areas, depending on the particular kind of contact concerned and on the nature of the electric circuit. 7

3,042,778 l atented July 3, 1962 It is well-known that electrical discharges or arcs can produce marked erosion of electrodes used for contact; the make and break contacts in, the ignition system of internal combustion engines is an outstanding example. Hence, if the operating conditions of the contact are such that an arc occurs (as when the potential between the electrodes equals or exceeds the ionization voltage of the gas or vapor between the electrodes) electrode erosion is to be expected. Material eroded from one electrode usually is transferred by the arc to the other electrode, producing wear and disfigurement. Such transfer of electrode material is known as arc transfer. 1

The useful life of the electrodes, which is generally limited by are transfer, depends on the intensity, dwell time and frequency of occurrence of the arc, and on the contact area and material of the electrodes. Of these factors, are intensity controls the erosion rate of the electrodes and is a function of circuit power; the other factors affect the degree of erosion over a period of time and are functions of the design and operating conditions of the electrodes. In communication circuits where power is low, erosion of the electrodes is relatively slow compared to the rate in higher power systems where potentials between electrodes can be hundreds and even thousands of volts. The electrodes in the latter would soon disintegrate without effective means for controlling the are.

Whenever direct current is broken, arc transfer tends to develop a pit, or crater, in the anode electrode and deposit some or all the eroded material on the cathode electrode to produce an excrescence or growth. The crater and growth are seldom exact counterparts of one another, hence, the growth is unlikely to be completely contained or enveloped in the crater when the electrodes meet to make electric contact. It is clear that disfigurement of the electrodes by the crater and growth formations can cause failure of the contact due to high resistance'connection, mechanical locking or to simply wearing away of one of the electrodes. Also, it must be remembered that in some light duty applications, as in communication networks, electrode travel is frequently very short and growths projecting only a few tenths millimeters from the electrode can render the contacts ineffective. In critical applications where extreme requirements of continued efficiency are specified, the customary solution in the past has. been not to attempt to solve the problem but to postpone it by using precious metals for contact electrodes. This is frequently impractical because of the extra expense, expense which is not justified in many applications by the longer life thereby obtained. A further technique has been to enclose the electrodes to prevent atmospheric contamination. At the same time, the enclosing means might be evacuated, pressurized with a gas, or oil filled. Another solution in some applications has been to recognize the defects of the. contacts used in the past and surrender to their known limitations by making the system more accessible and easier to service when required.

' Turning now from the general problem of deterioration to the problems of a specific application, in a conventional automobile ignition system the circuit make and break electrodes, hereinafter also referred to as breaker a points, are required to interrupt as abruptly as possible with the basically simple electro-mechanical ignition sys- 3 tern, it is logical and desirable that the breaker points have as long a useful life, and be as free from service requirements as economic limitations and the state of the art will permit. Heretofore, in order that peak perform ance of the engine may not be hampered by ignition dlfficulties, breaker points have required relatively frequent attention and replacement, usually by trained technicians. In addition to the expense, loss of the use of the vehicle or equipment, and the inconvenience and bother such service entails, the problem of adjustment and replacement is complicated by the fact that the breaker points are fre quently located in confined spaces, congested and dlffiClllll of access. It is not surprising, therefore, that there has been a strong tendency to put off or delay servicing the breaker points until long after the ignition system has ceased to function efliciently and engine performance has become impaired. It follows that an inexpensive electrical contacting device having appreciably longer life than the presently conventional breaker points, and requiring far less service, is an advancement in the state of the art and an improvement in the ignition system commonly used for internal combustion engines.

The contacting area of metallic electrodes for making and breaking 'a circuit is normally proportional to the circuit power, and individual arc discharges generally do not fill the region between the contacting surfaces. For example, the feet of an arc discharge between ignition breaker points occupy but a very small portion of the contacting area provided and usually at a location corresponding to the shortest distance between the contacting surfaces at the instant of separation.

Irrespective of ignition circuit parameters, it is of primary importance to maximum life and operating efficiency of the breaker points that the contacting surfaces be flat and constrained to meet -invariably in concentric and coplanar relationship when making electric contacts. In this optimum geometric alignment of contacting planes, the arc discharge normal for each parting of the breaker points can occur indiscriminately and at random over the entire contacting area. Unless influenced by factors other than electrode alignment, it follows that the average disposition of the arc discharges results in a distribution that is uniform over the entire area of contacting surface. It is evident, therefore, that the erosion rate per unit area of contacting surface is then at the minimum.

. A small axial misalignment of otherwise optimally aligned contacting planes is relatively unimportant since contacting area is not appreciably diminished and distribution of arcing is not atfected. It is evident, however, that'the slightest deviation from a true coplanar meeting of flat contacting surfaces will not only reduce the contacting area considerably but concentrate arcing at a small sector at the rims of the contacting surfaces where the breaker points must, perforce, come together. The ensuing acceleration of erosion at the localized contacting area prematurely widens the initially adjusted gap between the breaker points and transfers material from one breaker point to the other at arate which produces surface craters and growths in a comparatively short time. One started, this deterioration of the contacting surfaces increases at an increasing rate and malfunction of the ignition system occurs much sooner than when the contacting surfaces come together squarely. The majority of breaker point replacements are premature for this reason.

The customary mode of making and breaking the primary ignition circuit is to have one of the breaker points firmly aflixed to the end of a pivoted rocker arm, the point making a spring-loaded contact with a mating point firmly afifixed to a relatively stationary support. A cam rotating with the engine displaces the arm against the spring causing the breaker points to be briefly separated.

It is apparent in this arrangement that in order for flat contacting surfaces to meet consistently in exact coplanar relationship, it is essential that the relative disposition of the members supporting the breaker points be precisely established and maintained and actuation of the movable member be unvarying. Heretofore, the adequacy in design and the manufacturing precision necessary to satisfy these requirements have been precluded by economic considerations. It follows that optimum and enduring alignment of fiat contacting surfaces cannot be assured in the conventional breaker point arrangement and breaker points having such surfaces are subject to early deterioration.

In order to permit some tolerance in alignment, it is common for one or both contacting surfaces of conventional breaker points to be slightly crowned, that is, slightly convex. Since by this expedient contacting area is sacrificed, the operating life and efliciency of the breaker points are reduced, and the need for service is increased. Obviously, such compromise is not a satis-.

factory solution to the problem.

While a coplanar meeting of flat contacting surfaces predisposes uniform distribution of the arc discharges over the entire contacting area, inhomogeneities, whether on the surface or within the structure of the electrode material, often tend to form a nucleus for local are dis charges. Heretofore, contacting devices such as ignition breaker points have been Without means for deterring development of a nucleus of this sort, in the course of which local arcing progresses from a sporadic stage to a persistent state. The subsequent increasing rate of local erosion culminates in premature failure of the electrodes in a manner similar to that induced by imperfect alignment of contacting planes. It'follows that while optimum alignment is essential to uniform distribution of arc discharges over the contacting planes, discriminative arcing leading to destruction of the electrodes can be initiated by a cause other than geometric.

When contacting surfaces meet without sliding or wiping, wear from mechanical abrasion is generally a very insignificant factor in the life of the electrodes. Migration of particles from one electrode to the other when the electrodes are in contact, a phenomenon variously known as fine transfer, bridge transfer, bridge erosion, or by other terms, is ordinarily also an unimportant factor in electrode life. Arc transfer, then, is by far the greatest cause of electrode deterioration and it is patent that were arcing completely eliminated from between the contacting surfaces, electrode life and replacement would cease to be matters for practical consideration.

It logically follows that electrode life will'be lengthened to the extent that arcing intensity can be reduced.

The capacitor normally connected across ignition breaker points reduces the intensity of the arc discharges considerably, and, in so doing, causes the spark coil primary circuit of the ignition system to be broken with suflicient speed to generate an ignition voltage in the spark coil secondary. However, from the fact that breaker point life has heretofore been limited by the ravages of arc discharges, it is obvious that the arcingwhich persists despite connection of the capacitor is of an intensity level sufficiently high to be quite damaging. The efficacy of a shunt-connected capacitor in reducing arcing intensity across the breaker points is limited by required operating conditions of the breaker points, and by circuit parameters bearing on desirable critical damping of the spark coil primary circuit. Any further reduction in arcing intensity has not heretofore been possible without repercussions on size, complexity or cost of the ignition system.

In addition .to having deleterious physical effects on breaker points, arcing can also reduce the operating etficiency of the ignition system. This occurs whenever persistence of the are from the instant the breaker points open is longer than the time required for collapse of the spark coilmagnetic fields On such occasions, arcing'retards collapse of this field and lowers the ignition voltage induced in the spark coil secondary.

It is one'object of my invention, therefore, to provide a contacting arrangement wherein the planes of two flat contacting surfaces are caused to meet automatically and invariably in exact coplanar relationship from the beginning of service throughout the useful life of the individual electrodes, for the purpose of (l) assuring maximum contacting area, (2) extending electrode life, and (3) improving efiiciency of the electric contact. A second object of my invention is to provide means for preventing arc discharges from becoming localized on flat contacting surfaces due to causes other than failure of flat contacting surfaces to meet in true coplanar relationship. A third object of the invention is to provide means that will, without changing circuit parameters, reduce to a lower level of intensity arcing which persists between contacting surfaces notwithstanding connection of a capacitor of optimum electrical value across the electrodes, for the purpose of (1) reducing the rate of erosion of the contacting surfaces and thereby further extending electrode life, (2) permitting closer spacing of electrodes than has heretofore been practical, and (3) affording more abrupt termination of current flow in a circuit in which the speed of termination has heretofore been limited by intensity of arcing at the contacting surfaces.

A fourth object of my invention is to achieve the aforesaid objects by a simple, economical, highly compact arrangement which when necessary can be serviced by a technician of ordinary skill.

In the accomplishment of these and other objects of my invention, and relating more specifically but not exclusively to application to the common ignition system for internal combustion engines, Iprovide a ring-shaped electrode having a flat contacting surface, at the end of a rocker arm. The relatively stationary contacted electrode resembles the movable electrode and is a part of an assembly of parts having a hemispherical shape. The curved portion of the hemispherical assembly, hereinafter referred to as hemisphere, is positionally seated in a socket contained in a supporting member, in the manner of a ball and socket disposition.

A feature of the invention is retention of the hemisphere in its socket by magnetic attraction. Another feature isthat by virtue of such magnetic retention, the diametric plane of the hemisphere, of which the stationary electrode is a part, may be readily tilted inany direction. A further feature is that the stationary electrode will be automatically aligned when contacted by the flatcontacting surface of the movable electrode, regardless of any changes in the plane of the latter. A still further feature of the invention is that during an arc discharge between the electrodes, the electrons and ions which constitute the arc, referred to hereinafter also as arc elements, are acted upon by a magnetic force in a manner which deflects the are as a whole from a normally fixed position between the electrodes and causes it to move in a circular direction on the contacting surfaces of the electrodes throughout the time of its endurance.

Still another feature of my invention is that during an arc discharge, the are elements are urged by a magnetic force into a longer than normal path between the electrodes, hence the arc discharge is extinguished sooner during separation of the contacting surfaces and erosion of these surfaces is correspondingly reduced These and other objects and features of the invention will best be understood and appreciated from the following descriptionof a preferred embodiment thereof, selected for purposes of illustration, and shown in the accompanying drawings in which: 1 FIG. 1 is a diagrammatic andschematicrepresentation of a breaker point arrangement of a typical automobile ignition system; a

' FIG. 2 is an enlarged cross-section of electrode elements embodying'the present invention;

FIG. 3 is a topview of a hemisphere embodying the stationary'electrode and a magnet, showing the direction of magnetic flux lines existing at the plane of the stationary electrode; a

FIG. 4 is a simplified cross-section of the hemispherical embodiment of the stationary electrode and the magnet, seated in a socket contained in a support made of magnetically permeable material. The direction of magnetic flux lines created by the interrelationship of the magnetic parts of the hemisphere and the support is shown by dash radial arrows; and

FIG. 5 is a simplified cross-section of a variation of the arrangement shown in FIGURES 3 and 4.

FIGURE 1 shows in simplified schematic and diagrammatic representation the usual breaker point system. Arm 2 is pivotally mounted on shaft4. At the end of arm 2 the contacting surface 6 of movable electrode 8 is positioned to meet the corresponding contacting surface 10 of fixed electrode 12. In the usual breakerpoint system, this fixed electrode is secured to a grounded member or bracket as shown. Spring 14 tends to keep the contacting surfaces 6 and 10 together. However, as cam 16 rotates, the lobes A, B, C, D, and E and F continuously cause arm 2 to be raised slightly, momentarily separating electrodes 8 and 12. When the electrodes are together the voltage of battery 18 causes current to flow in the series circuit comprising primary coil 20, spring 14, arm 2, through the electrodes 8 and 12 to ground and return. The momentary opening of electrodes 8 and 12 causes an abrupt cessation of current flow and the collapsing magnetic field of primary coil 20 induces an ignition voltage in secondary coil 26. The counter generated in primary coil 20 by the collapsing magnetic field attempts to maintain the current flow and if the breaking of the circuit is sufficiently fast a considerable voltage is induced across the primary. This voltage, although transient, causes atmospheric gases to become ionized between contacting surfaces 8 and 12 at the instant of parting and produce a not insignificant are discharge. As time elapses from the instant the arc is struck, the distance between the electrodes 8 and 12 increases and the voltage between electrodes decays and the arc becomes extinguished.

When the primary circuit is critically damped, or nearly so, capacitor 22 absorbs a considerable portion of the high transient voltage that tends to appear across electrodes 8 and 12 whenever the circuit is broken. However, while arcing intensity is thereby reduced to a level permitting the magnetic field of primary coil 20 to collapse with a speed sufficient to induce an ignition voltage in secondary 26, the remaining intensity is usually severe enough to erode contacting faces 6 and 10 at a rate that necessitates frequent servicing or replacement of the electrodes.

In my invention the make and break actuation of the electrodes is similar to that shown in FIG. 1, but the electrode contacts are of markedly different configuration and construction from those heretofore employed. Referring now to FIG. 2,.electrode 28, affixed to arm 2 (shown in phantom), is ring-shaped and constructed of a suitable non-magnetic metallic material having a contacting plane. 30 indicated at XX. Arm 2 is of nonmagnetic material, at least in the vicinity of electrode 28, in order that it may have no influence on a magnetic field near this electrode. The other electrode comprises a generally hemispherical electrode buton 32 which is pivotally mounted in a ball-joint arrangement in a socket 34 of a support 36. The latter is secured to a-grounded' member or bracket in the same way as electrode 12 of FIG. 1.

In the preferred embodiment described herein, the assembly of electrode button 32 is composed offour firmly joined: parts. Center part 38 is a magnetic core of high energy permanent magnet material such as Alnico- 5.

Immediately surrounding c0re38 is a ring-shaped electrode 48 of suitable non-magnetic metallic material upon the surface 40 of which the surface 30 of electrode 28 makes physical and electrical contact. At the peripheral edge of the hemispherical button 32 is a ring 42 having essentially a triangular cross-section and made of a material having high magnetic permeability such as Norway iron. Completing the hemispherical shape and volume of button 32 is a fourth part 44 made of a non-magnetic but preferably electrically conducting material.

The diametric plane of hemispherical button 32 consists of the surface of one end of core 38, surface 40 of ring electrode 48 and a surface of ring 42, all being on a common plane YY which is perpendicular to the axis of the magnetic core 38.

The support 36 can be made of any material having good electrical conductivity and high magnetic permeability, such as Norway iron. The socket or cup 34 formed in support 36 has a configuration to suit button 32, and the depth is desirably somewhat shallower than the button radius so that plane Y--Y is somewhat above surface 46 of support 36 to facilitate measurement and adjustment of electrode spacing.

Since button 32 is retained in socket 34 of support 36 only by magnetic attraction, it is free to pivot in its socket in any direction. It will be noted from FIG. 2 that when arm 2 presses electrode 28 against electrode surface 40, which is coincident with plane Y-Y of button 32, the latter will adjust itself in its socket until its plane Y-Y is coplanar in its meeting with plane XX of electrode 28. The alignment of plane Y-Y with plane XX is thus automatically maintained and the full area of the annular contacting surface 30 of electrode 28 makes electrical connection with a corresponding area on the annular contacting surface 40 of ring electrode 48. The inside and outside diameters of ring electrode 48 are somewhat smaller and somewhat larger respectively than the equivalent diameters of ring electrode 28 to minimize the possibility of the latter touching either the center core 38 or the outer, peripheral ring 42. It is to be understood that the areas of surfaces 30 and 40 are to be properly proportioned with respect to the power of the circuit. It is also to be understood that button 32 is constantly in good electrical contact with support 36.

Since the flat contacting surfaces 30 and 40 are constrained to meet always in true coplanar relationship, maximum contacting area is assured. Unless influenced by causes other than mis-alignment, arc discharges coincident wtih separation of these surfaces will occur indiscriminately and at random over the entire area of the contacting surfaces. Erosion due to are transfer is therefore not confined to some local area on the contacting surfaces, which condition, as has been explained, is a defect common in ordinary contacting devices, leading generally to malfunction of an ignition or another type of circuit. On the contrary, the spreading of arc discharges over the entire contacting area of the electrodes results in minimizing the erosion rate per unit area of contacting surface, and aids materially in preserving the contacting surfaces and extending electrode life. Furthermore, contact resistance tends to be lower and more uniform due to the entire contacting area meeting with equal pressure at all points. It is clear that the purposes of the first mentioned object of my invention are accomplished in the manner just described.

In FIG. 4 it can be seen that the path of the magnetic field of magnetic core 38 is through a portion of the support 36, through the ring 42, and radially across the exposed surface 40 of ring electrode 48 .at the plane YY of button 32. As indicated by the dasharrows in FIG. 3 there exists at the surface Y-Y a radial magnetic field which bridges an annular gap 50, the gap being across the surface 40 of ring electrode 48. ,Due to the crosssectional shape of ring 42, the path of minimum magnetic reluctance coincides with the exposed surface 40 of ring electrode 48, hence the plane of the lat-ter co that part of the magnetic field having the shortest path' and the greatest field strength.

Arc discharges occurring between electrode surfaces 39 and 40 at the instant of break must take place wholly within the annular magnetic gap 50 and on a plane where the magnetic field is strongest. The electrons and ions which constitute an arc discharge migrate from one electrode to the other in opposite directions in the electric field between surfaces 30 and 40"but in a common path or beam that is normally perpendicular to the plane of the radial magnetic field bridging the annular gap. Be cause of the well known affect of a magnetic field on charged moving particles, the are elements are subjected to a force which deflects them in a common sidewise direction that is ever perpendicular to the radial flux lines in the annular gap. An arc discharge as a whole, from its inception until its extinction, is therefore coersed by the magnetic field to digress from a normal fixed path between the electrodes and effect a circular excursion over electrode surfaces 30 and 40 in an orbital trend about core 38. Erosion and vaporization of electrode material is hindered by the rapid movement of the arc feet across the contacting surfaces and the arc discharge tends to pass into a much less harmful glow discharge before becoming completely extinguished by the weakening of the electric field as the gap between surfaces 30 and 40 is widened.

It is evident that control of arc discharges in this manner inhibits formation of a nucleus for local are discharges that could otherwise be created by inhomogeneities on the surface or within the structure of the electrode material, or by any other cause against which positive coplanar alignment of surfaces 30 and 40 is ineffective. By this means, then, is the second object of my invention accomplished.

Since the electrons and ions of any arc discharge between electrodes 28 and 48 are exposed to the magnetic deflecting force in annular gap 50 during the entire time of their transit from one electrode to the other, it is evident that the deviation from their normal direct path between the electrodes becomes increasingly greater with progress in transit and that the deflection is maximum at the instant of impingement on the electrode toward which they migrate. The electrons, having much less mass, are deflected considerably more than the ions and into an elongated path that has a tendency to spiral around core 38. The extent to which the deflected electron path spirals is a function of the ratio of the electric field strength between the electrodes to the magnetic field strength in annular gap 50. When the magnetic field is strong compared to the electric field, a condition which should be accentuated-as greatly as possible by design, the spiraling characteristic is considerable and the electron path is correspondingly lengthened between the electrodes.

It is to be remembered that ionization of a region between electrodes requires free electrons to be present in that region. Because of the deflection of the electrons from their normal direct path between electrodes, ionization of this path is precluded and occurs instead in the diverted electron path. It is evident, therefore, that an arc discharge, as a whole, for a given gap width between electrodes 28 and 38 is stretched out and elongated to the extent that the deflected electron path is longer than the normal path.

It is to be understood that such elongation of .an arc discharge occurs simultaneously and in combination with the reaction of the arc discharge to the magnetic field in annular gap 50 wherein the arc discharge as a whole tends to orbit about 38 Wlth itS feet moving in a circular direction on electrode surfaces 30 and 40, as has been previously explained. a

In the conventional breaker point arrangement and other common contacting methods, the arc is drawn out and the electric field becomes progressively weaker as the gap between electrodes is widened. When the gap is widened to the extent that the electric field is too weak to sustain ionization of the extended arc discharge, the arc is suddenly extinguished. In my invention, however, in addition to its other features the arc discharges between electrode surfaces are lengthened or stretched out to extinguishment not only by widening of the gap between these surfaces but by deflection of the electrons normally present in arc discharges. It is evident, therefore, that for a given speed of separation of the electrodes, and for a given electrical potential across them, arc discharges are extinguished sooner after parting of the electrodes'and at a narrower gap between the electrode surfaces. It follows that by thus lessening the dwell of arc discharges between electrodes, erosion of the electrode contacting surfaces is reduced and life of the electrodes is increased. Furthermore, extinguishment of arc discharges at lesser separation of the electrodes permits a closer sp-acingthan has heretofore been practical, resulting in less wear on actuating parts such as cams, cam followers, pivot shafts and bearings, etc., in less noise, contact bounce, and in more precise and uniform timing, particularly at high rates of speed in making and breaking a circuit. An additional advantage is more abrupt termination of current flow upon separation of the electrodes, thus resulting in higher ignition efficiency. In augmenting, by the means explained, the distortion and extension of arc discharges normally occurring when electrodes are separated, the purposes in the third object of my invention are accomplished.

A variation in design of electrode button 32 and support 36 is shown in FIG. 5. The electrode indicated at 52 in FIG. is identical to that shown in FIG. 2 except that cylindrical core 54 of the variation is made of a material having a high magnetic permeability such as Norway iron; support 56 would be made of a high energy permanent magnet material such as Alnico 5, magnetized in a manner to produce a field through core 54 as indicated by the arrows in FIG. 5.

A hole 58 in the bases 36 and 56 permits the contact button to be conveniently poked out of its socket with a thin rod when removal is necessary.

While the foregoing description is in terms of using permanent magnetic materials, the same results can be achieved with electromagnetically created fields. Other minor variations of this preferred embodiment will be apparent to those skilled in the art; and, therefore, it is not my intention to confine the invention to the preclse form herein shown, but rather to limit it in terms of the appended claims.

I claim:

1. An electrical contact device comprising first and second contact members having first and second contact surfaces respectively, said first surface being non-magnetic, said second member having a magnet for producing a magnetic field between said contact surfaces and means for concentrating said magnetic field in substantially coplanar relation with said second contact surface, said magnetic field arranged to cause movement of the path of arc-carrying ions in a direction perpendicular to the axes of saidmembers while simultaneously causing distortion of said path of arc-carrying ions between said members.

2. An electrical contact device comprising first and said end face, a single magnet, and means cooperating with said magnet to provide an annular magnetic field confined. along said surface. 3. An electrical contact device comprlsmg a hermspherical contact member pivotally seated in a socket member of magnetically permeable material, said hemispherical contact member comprising a magnetic core coaxial with the principle hemispherical axis, a non-magnetic ring surrounding said core, and a ring of permeable magnetic material at the periphery of said non-magnetic ring, said member hemispherical contact having a planar contact surface and a radial magnetic field concentrated at said contact surface.

4. A hemispherical contact member having a planar contact surface and comprising a core of magnetically permeable material surrounded by a ring of non-magnetic material, and a magnetically permeable material forming a ring at the periphery, said member having a radial magnetic field at the contact surface thereof when seated pivotally in a socket formed in a magnetic material.

5. An electrical contacting device having first and second self-aligning contact electrodes, said first contact electrode having an annular substantially flat contact surface, said second electrode having a substantially hemispherical body with a round substantially flat contact surface, said hemispherical body pivotally supported in a socket of complementary configuration and retained for relative movement therein by direct magnetic attraction thereto, whereby substantially coplanar surface contact is achieved between said contacting surfaces, said hemispherical body comprising a center core of permanent magnetic material, a body portion including the contact surface of said hemispherical body surrounding said core, said body portion and the contact surface of said hemispherical body made up of non-magnetic, electrically conductive material, and a peripheral ring surrounding said contact surface composed of magnetically permeable material.

6. Self-aligning contact electrodes comprising first and second electrodes having first and second planar contacting surfaces respectively, said first surface made of nonmagnetic material, said second electrode including a supporting structure having a socket portion, a ball portion pivotally seated in said socket portion, and a magnet exerting a magnetic force on both portions whereby to retain said ball portion in said socket portion, said magnet disposed so that most of the path of its magnetic field is through said ball and socket portions, with a portion of said path extending radially across said second planar contacting surface.

7. Self-aligning contact electrodes comprising first and second electrodes having first and second planar contacting surfaces respectively, said second electrode including a supporting structure having a socket portion, a ball portion pivotally seated in said socket portion, and a magnet exerting a magnetic force on both portions whereby to retain said ball portion in said socket portion, said second surface including a non-magnetic portion and said electrodes mounted so that said first electrode contacts said second electrode only at said non-magnetic portion. 8. Self-aligning contact electrodes comprising first and second electrodes having first and second planar contacting surfaces respectively, said second electrode including a supporting structure having a socketportion, a ball portion pivotally seated in said socket portion, and a mag- ,net integral with said ball portion exerting a magnetic force on both portions whereby to retain said ball portion in said socket portion.

9. Self-aligning contact electrodes comprising first and second electrodes having first and second planar contact surfaces respectively, said second electrode including a supporting structure having a socket portion, a ball portion pivotally seated in said socket portion, and a permar 1 1 at a point in the bottom thereof for insertion of a tool for poking said ball portion out of said socket portion.

10; A hemispherical contact member having a planar diametric contact surface and comprising, a magnetic core coaxial with the principal hemispherical axis, a non-magnetic ring surrounding said core and forming at least part of said contact surface, and a ring of magnetically permeable material at the periphery of said non-magnetic ring, said contact member having a magnetic field which passes through and is shaped by said ring of magnetically permeable material with the path of minimum magnetic reluctance coinciding with said contact surface, whereby said magnetic field is concentrated at and extends radially across said contact surface.

11. Self-aligning contact electrodes comprising first and second electrodes having first and second planar contacting surfaces respectively, said second electrode including a supporting structure having a socket portion, a ball portion pivotally seated in said socket portion, said ball portion comprising a center core of a material of high magnetic permeability and a peripheral ring of high magnetic permeability surrounding said second contact surface, and a magnet integral with said socket portion 12 exerting a magnetic force on both portions whereby to retain said ball portion in said socket portion, said magnet disposed so that most of the path of its magnetic field is through said ball and socket portion with a portion of said path extending radially across said second planar contacting surface.

References Cited in the file of this patent UNITED STATES PATENTS 1,771,905 Uher July 29, 1930 2,334,562 Latta Nov. 16, 1943 2,411,892 Peters Dec. 3, 1946 2,411,893 Peters Dec. 3, 1946 2,611,059 Imrnel et a1 Sept. 16, 1952 2,671,148 Schulenburg Mar. 2, 1954 2,725,446 Slepian Nov. 29, 1955 FOREIGN PATENTS 494,131 France May 22, 1919 655,491 Great Britain July 25, 1951 Rankin May 16, 1939 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent N0. 3,042,778 July 3. 1962 Albert E, Anderson It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 1O line 6 for "member hemispherical contact" read hemispherical contact member.-,.

Signed and sealed this 20th day of November 1962 (SEAL) ,Attest: A r

[ ERNEST w. SWIDER VI L. LA D Attesting Officer Commissioner-"of Patents 

